Tin(II)-based halide perovskites have shown promises in lead-free and mixed tin(II)-lead ideal-bandgap photovoltaic applications. Nonetheless, they notoriously suffer from oxidation in oxygen environments, thereby sustaining rapid self-doping during synthesis and further material degradation in post-synthesis stages. As such, enhancing the chemical stabilities of tin(II) halide perovskites is imperatively crucial for further advancement of any relevant eco-friendly and low-bandgap photovoltaic technology. Here, we demonstrate that hydroquinone (H₂Q), a chemically reductive organic molecule, can effectively improve the stability of perovskite methylammonium tin(II) iodide (CH₃NH₃SnI₃) in air environments, as proved by X-ray diffraction and X-ray photoelectron spectroscopic studies. Furthermore, luminescence longevity of H₂Q-added CH₃NH₃SnI₃ film is much greater than its undoped pristine counterpart in ambient air, as unambiguously evidenced by the evolution of their time-dependent PL spectra. Our work provides a practical clue to stabilizing tin(II)-based perovskite optoelectronics.

XPS Sn 3d spectra of MASnI<sub>3 </sub>(a, c) and H<sub>2</sub>Q:MASnI<sub>3</sub> (b, d) measured after aging in dry air (RH<5%) for 0 hour, 1 hour respectively. (e) Comparison of Sn<sup>4+</sup> content in pristine MASnI<sub>3</sub> and H<sub>2</sub>Q:MASnI<sub>3</sub> before and after 1-hr oxidation in dry air.

XPS Sn 3d spectra of MASnI₃(a, c) and H₂Q:MASnI₃ (b, d) measured after aging in dry air (RH<5%) for 0 hour, 1 hour respectively. (e) Comparison of Sn⁴⁺ content in pristine MASnI₃ and H₂Q:MASnI₃ before and after 1-hr oxidation in dry air.

Evolution of time-integrated PL spectra in air for pristine MASnI<sub>3</sub> (a), H<sub>2</sub>Q:MASnI<sub>3</sub> (b), and PvPh:MASnI<sub>3</sub> (c) thin films. (d) Summary of PL peak intensities of the three types of tin(II) perovskite thin film samples.

Evolution of time-integrated PL spectra in air for pristine MASnI₃ (a), H₂Q:MASnI₃ (b), and PvPh:MASnI₃ (c) thin films. (d) Summary of PL peak intensities of the three types of tin(II) perovskite thin film samples.

Wei Huang

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